首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   151篇
  免费   2篇
  国内免费   1篇
系统科学   5篇
理论与方法论   2篇
现状及发展   51篇
研究方法   18篇
综合类   77篇
自然研究   1篇
  2021年   1篇
  2018年   2篇
  2017年   5篇
  2016年   1篇
  2015年   2篇
  2014年   2篇
  2013年   2篇
  2012年   8篇
  2011年   16篇
  2010年   6篇
  2008年   7篇
  2007年   15篇
  2006年   10篇
  2005年   7篇
  2004年   10篇
  2003年   9篇
  2002年   6篇
  2000年   2篇
  1996年   2篇
  1993年   1篇
  1992年   1篇
  1990年   1篇
  1988年   3篇
  1986年   1篇
  1985年   1篇
  1982年   1篇
  1980年   2篇
  1978年   2篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1974年   4篇
  1973年   3篇
  1972年   4篇
  1971年   3篇
  1969年   2篇
  1968年   4篇
  1967年   2篇
  1945年   2篇
排序方式: 共有154条查询结果,搜索用时 31 毫秒
81.
Shima S  Krueger M  Weinert T  Demmer U  Kahnt J  Thauer RK  Ermler U 《Nature》2012,481(7379):98-101
The anaerobic oxidation of methane (AOM) with sulphate, an area currently generating great interest in microbiology, is accomplished by consortia of methanotrophic archaea (ANME) and sulphate-reducing bacteria. The enzyme activating methane in methanotrophic archaea has tentatively been identified as a homologue of methyl-coenzyme M reductase (MCR) that catalyses the methane-forming step in methanogenic archaea. Here we report an X-ray structure of the 280?kDa heterohexameric ANME-1 MCR complex. It was crystallized uniquely from a protein ensemble purified from consortia of microorganisms collected with a submersible from a Black Sea mat catalysing AOM with sulphate. Crystals grown from the heterogeneous sample diffract to 2.1?? resolution and consist of a single ANME-1 MCR population, demonstrating the strong selective power of crystallization. The structure revealed ANME-1 MCR in complex with coenzyme M and coenzyme B, indicating the same substrates for MCR from methanotrophic and methanogenic archaea. Differences between the highly similar structures of ANME-1 MCR and methanogenic MCR include a F(430) modification, a cysteine-rich patch and an altered post-translational amino acid modification pattern, which may tune the enzymes for their functions in different biological contexts.  相似文献   
82.
A map of the cis-regulatory sequences in the mouse genome   总被引:1,自引:0,他引:1  
Y Shen  F Yue  DF McCleary  Z Ye  L Edsall  S Kuan  U Wagner  J Dixon  L Lee  VV Lobanenkov  B Ren 《Nature》2012,488(7409):116-120
  相似文献   
83.
84.
Summary The local anesthetic effects of cocaine and one of its main metabolites norcocaine, were investigated comparatively on isolated ganglion cells of the marine gastropod,Aplysia californica. During a 1-hour-period, different action potential parameters such as amplitude, duration, maximum rate of rise were observed, which demonstrated that norcocaine exhibits a higher local anesthetic potency than cocaine.Acknowledgments. The authors are grateful to Dr M. R. Klee and Dr M. R. Park for helpful discussion. The work was partly supported by Österreichischer Fonds zur Förderung der wissenschaftlichen Forschung  相似文献   
85.
86.
87.
88.
After V(D)J-mediated translocations, signal joints are retained on one of the derivative chromosomes. We report here that such signal joints are highly reactive and constitute unstable genomic elements with potential oncogenic properties.  相似文献   
89.
90.
A microscopic quantum system under continuous observation exhibits at random times sudden jumps between its states. The detection of this quantum feature requires a quantum non-demolition (QND) measurement repeated many times during the system's evolution. Whereas quantum jumps of trapped massive particles (electrons, ions or molecules) have been observed, this has proved more challenging for light quanta. Standard photodetectors absorb light and are thus unable to detect the same photon twice. It is therefore necessary to use a transparent counter that can 'see' photons without destroying them. Moreover, the light needs to be stored for durations much longer than the QND detection time. Here we report an experiment in which we fulfil these challenging conditions and observe quantum jumps in the photon number. Microwave photons are stored in a superconducting cavity for times up to half a second, and are repeatedly probed by a stream of non-absorbing atoms. An atom interferometer measures the atomic dipole phase shift induced by the non-resonant cavity field, so that the final atom state reveals directly the presence of a single photon in the cavity. Sequences of hundreds of atoms, highly correlated in the same state, are interrupted by sudden state switchings. These telegraphic signals record the birth, life and death of individual photons. Applying a similar QND procedure to mesoscopic fields with tens of photons should open new perspectives for the exploration of the quantum-to-classical boundary.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号